Heat exchanger



March 27, 1956 H. G. MUELLER 2,739,795

HEAT EXCHANGER Filed April 19, 1954 5 Sheets-Sheet l i m M 1 a l. j 2' m l: I m

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March 27, 1956 MUELLER 2,739,795

HEAT EXCHANGER Filed April 19, 1954 5 Sheets-Sheet 3 am n ewe IN VEN TOR.

March 27, 1956 H. G. MUELLER 2,739,795

HEAT EXCHANGER Filed April 19, 1954 5 Sheets-Sheet 4 INVENTOR.

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7 March 27, 1956 H. G. MUELLER HEAT EXCHANGER 5 Sheets-Sheet 5 Filed April 19, 1954 INVEN TOR. mm

United States Patent HEAT EXCHANGER Herman G. Mueller, Erie, Pa.

Application April 19, 1954, Serial No. 424,006

7 Claims. (Cl. 257-441) This invention relates generally to conduction heat exchangers from a gas to a liquid or vice versa and more particularly to interstage and after coolers used with gas compressors.

The conventional construction of this type of exchanger generally consists of long parallel tubes mounted in a cylindrical casing having a fixed tube sheet on one end and a movable tube sheet on the other end, packed to allow for expansion. Multiple perforated baflles, through which the tubes pass are arranged to circulate the fluid outside the tubes back and forth across the tubes and from one end to the other.

The heat transfer surface required for conveying the heat from the gas to metal is many times that required for conveying the heat from metal to liquid. This is also true for conveying heat in the opposite direction from the metal to gas. Since the surface on the outside of the tubes is only a small percentage larger than the surface on the inside, the length of tubing and volume of the heat exchanger as a whole becomes large and cumbersome in order to provide suflicient tube surface for transferring the heat from the gas to the metal (or vice versa), regardless of whether the inside or outside surface of the tubes is so used.

When such conventional tubular heat exchangers are used for interstage and after coolers on multistage compressors, they are very large in size compared to the compressor served, can be mounted only with difficulty and extra piping and in general make an unsightly and top-heavy appearance and their cost becomes uneconomical.

Radiator cores have been used in some instances with reduction in size and cost and improved appearance. Such cores are conventionally made of flattened copper tubing mounted in parallel and passing through perforated continuous fins at right angles to the tube. The liquid is passed through the tubes and the gas around the tubes and between the fins, thus giving the desired much greater surface for heat transfer from gas to metal. The tubes are usually soldered into the fins and into the liquid manifolds at either end of the tubes. This construction is widely used where the gas is at atmospheric pressure and for limited temperatures which will not melt the solder.

Where the gas is under pressure as in compressor inter and after coolers, such cores are vulnerable due to melting of solder in case the cooling liquid fails to circulate for any reason and because the gas pressure may collapse the flattened tubes. Such flattened narrow tubes are also difiicult to clean free of scale or deposits from the liquid on the inside of the tubes and carbon and oil deposits from the gas on the fins and outside of the tubes.

In recent years, tubes with fins at right angles and radial to the tube center line have become available. In some cases the fins are soldered to the tubes but the preferred type are those where a spiral fin is spun ice directly from a heavy walled tube making the metal of the fin and tube integral with no joint between them and no solder. Such tubes are now available with outside to inside surface area ratios from 2 or 3 minimum to 18 to 20 maximum.

Such tubes will withstand heavy external gas pressures without collapsing. The fins can be stripped off at either end and the bare tube rolled into the liquid manifold without the use of soldered joints. The tubes are circular and not flattened so that they are readily cleaned.

The difficulties encountered in applying such fin tubes to heat exchangers Where the external fluid is under pressure, are to arrange them in a simple, practical, safe and economical way.

It is, accordingly, an object of my invention to provide an external casing in which is assembled a removable core consisting of multiple fin tubes, giving a large surface area within comparatively small overall external dimensions for convenient and compact mounting on compressors or pumps.

Another object of my invention is to provide an external casing of economical construction capable of holding safely heavy gas pressures and temperatures, such as used in compressor after coolers, and which will give the necessary gas flow areas through the fins of the fin tubes in a continuous streamlined passage with a minimum of turns and pressure loss. The casing is also provided with suitable openings for assembly and removal of the fin tube core. It is also provided with a suitable condensation removal device. It is also shaped and formed for convenient mounting on a compressor or pump without an unsightly appearance.

Another object of my invention is to provide a removable core consisting of multiple fin tubes rolled into liquid manifolds, so arranged that any number of tubes can be used to convey the liquid inside the tubes in parallel for optimum liquid capacities and velocities and with a minimum pressure loss.

Another object of my invention is to arrange the mounting of the fin tubes in the core so that casing, tubing and manifold expansion and constraction with temperature changes is provided for without the use of floating packed heads.

Another object of my invention is to eliminate all use of soldered joints.

Another object of my invention is to provide semicircular fin tube forms which give a helical flow of the liquid in the tubes and improved metal to liquid heat transfer.

Another object of my invention is to provide short lengths of fin tubes readily accessible and short enough for easy cleaning internally.

Another object of my invention is to provide a complete counterflow of gas and liquid which will give the optimum heat transfer with a minimum of surface.

Another object of my invention is to provide com pressor interstage coolers suitable for mounting on compressors with one or more cylinders per stage and keep the internal core readily accessible and removable. Also to provide compressor after coolers suitable for mount ing in the pipe line and keep the internal core readily accessible and removable.

Another object of my invention is to provide a construction which can be mounted without injury on compressors or pumps having vibrations to which conventional long straight tube exchangers have proven very vulnerable because of tube wear and failure where they pass through the baflles.

Other objects of my invention will become evident from the following detailed description, taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a side elevational perspective view of an illustrative embodiment of my novel heat exchanger arranged horizontally for cooling the discharge gas from three low pressure cylinders of a vertical in line compressor, extracting moisture condensate and delivering the cooled gas to the single high pressure cylinder.

Fig. 2 is a side elevational view with parts broken away to show the internal arrangement of the fin tube core, condensation removal baffle and sump and the arrangement of liquid piping.

Fig. 3 is a side perspective view of a cast core manifold split in a horizontal plane through its center line and with the upper half lifted to show the internal liquid baffle and porting arrangement for multiple parallel and series passage of the liquid through the fin tubes.

Fig. 4 is a side elevational view of the manifold shown in Fig. 3 with the two halves bolted together and the fin tubes mounted and in part cut away.

Fig. 5 is a cross-sectional view taken on the line 5-5 of Fig. 4.

Fig. 6 is a crosssectional view enlarging from Fig. 5, the detail of the fin tube rolled into the manifold.

Fig. 7 is a side elevational view of a manifold of shorter length and greater diameter with the fin tubes mounted and in part cut away. This is an alternate construction to that of Figs. 1 through 6 and illustrates the flexibility of tube arrangements to vary, as needed, tube surface, gas passage area and liquid passage area to obtain any desired over all dimensions most suitable for mounting on the compressor.

Fig. 8 is a cross-sectional view taken on the line 83 of Fig. 7.

Fig. 9 is a side elevational view of an intercooler of modified form mounted vertically on a two stage two cylinder angle type compressor.

Fig. 10 is a side elevational view of an after cooler mounted in a pipe line with the core removable from either end.

Referring now to the drawings, Fig. 1 shows first stage compressor cylinders 1, discharging into a common manifold 2, connected by a flanged joint 3, to the inlet nozzle 4, of inter cooler casing 5. At either end of the cylindrical casing 5 is a flanged removable cover 6, on each of which is a stuiling box 7 with gland 8 through which the inlet and outlet cooling liquid pipes 9 pass.

The liquid manifold, preferably made of cast metal, is in two halves (Figs. 3, 4) 10 and 11 bolted together with a gasket joint. The cooling liquid enters at one end through a tapped hole 12 at one end of the manifold, filling chambcr .13 in both halves of manifold 10 and 11. lt then passes out the drilled holes 14 into which are rolled one end of the first set of fin tubes 15 which are formed in semi-circles. The opposite ends of these tubes are rolled into holes 16. The liquid passes in parallel through all tubes rolled into holes 14 and 16 emerging into chamber 17. Each of the halves l0, ll of the manifold has semi-circular tubes 15 on its outer surface. From chamber 17 the liquid passes through a way 17a into adjacent chamber 18 and out through holes 19 into the second set of fin tubes 15. The flow of liquid proceeds as indicated by the arrows into final chamber 29 from where it exhausts through tapped hole 12:! at the other end of the manifold.

The halves ill ll of the manifold are symmetrical, each having a longitudinal wall 17b from opposite sides of which extend cross walls 170 which divide the interior of the manifold into a plurality of liquid chambers which are opposite each other and separated by the longitudinal wall 17b. At each end of the manifold is a single chamber tapped with the inlet and outlet holes 12, 12a. The other chambers are arranged in pairs with the ways 17:: between adjacent chambers of each pair and with the pairs staggered on opposite sides of the wall 17b. While all of the chambers are opposite each other, the ways 17a in the cross walls provide a zig-zag flow of liquid.

Thus it becomes apparent that with the construction shown any number of tubes can be used for parallel flow of the liquid in each pass.

The number of tubes and their size are selected to give proper liquid velocities through the tubes (3 to 6 ft./sec.) with the capacity of liquid needed. Thus as shown in Figs. 3, 4 and 5 the tubes are arranged with two deep radially and three deep longitudinally in each half of the manifold. This gives twelve tubes with parallel liquid flow. In these figures the heat exchanger is shown with five liquid passes. In Figs. 7 and 8 is shown a heat exchanger with four tubes deep radially and two tubes deep longitudinally giving sixteen tubes with parallel flow in each half of the manifold. Thus it is apparent that the construction provided is quite flexible and can be varied to give overall dimensions best suited to the application, such as small diameter long casings as shown in Figs. 3, 4 and 5 or larger diameters with short lengths as shown in Figs. 7 and 8.

The cap screws 22 which hold the two halves 10, 11 of the manifold together are also used to hold in place semi-circular metal rings 23 which serve to guide the manifold assembly when inserted into casing 5. They have also been found useful in protecting the fins 0f the tubes when the tubes are being rolled into the manifold or when other work is being done on the manifold assembly, such as hydrostatic test for leaks.

The hot gas or air to be cooled enters the casing 5 through entrance nozzles 4 and circulates through the fins at right angles or transverse to the semi-circular tubes mounted on each half of the manifold. To the surface of the fin tubes is added the external surface of the manifold and its flanges which somewhat increase the heat transfer capacity of the exchanger.

The cooled gas or air emerges into chamber 24 (Fig. 2) at the cool end of easing 5 striking a baflle 25 which deflects the flow of the gas into drop leg chamber or sump 26 and into which is thrown moisture or other condensates before the cooled gas rises and passes out of casing 5 into the intake 27 of the next stage compressor cylinder 28. The condensate accumulates in drop leg 26 and is drained off by a trap 29. The baflle 25 is bolted on the inside casing 5 so that it can be removed for withdrawal of the manifold assembly from the cold end of the exchanger as well as the hot end as shown in dotted lines in Fig. 2.

Set screws 30, secured with fiber lock nuts 31 hold the manifold assembly rigidly in place in the casing 5.

The cooling liquid enters at the cold end of the exchanger and leaves at the hot end thus giving a purely couuterflow heat exchange between liquid and gas.

In Fig. 6 is an enlarged section through a fin tube and the manifold flange. The holes 14 are drilled and reamed to the outside diameter of the fin tube 15. One or two grooves 32 is machined in each hole and a bevel 33 machined on the inside end of each hole. The fin tube is then inserted and rolled or swaged with proper tools into the hole, the groove or grooves and flared into the bevel. This eliminates all soldered joining and forms a liquid tight seal capable of operating and remaining tight at high pressures and temperatures.

As shown in Fig. 10, substantially similar construction can be used when the exchanger is used as a .so-called pipe line after cooler. The hot gas enters from the pipe line 34 through flange 3 and nozzle 4 into casing 5 and emerges through flange 35 back into pipe line 36. A relief valve 37 is usually mounted on the casing 5 to protect it from over pressure due to failure of succeeding compressor stages.

An alternate arrangement of the exchanger used as an inter cooler with an angle type two stage two cylinder compressor is shown in Fig. 9.

In this case the exchanger is mounted vertically but otherwise quite similar to the aforementioned constructions.

What is claimed as new is:

1. In a heat exchanger, a longitudinally split manifold comprising mating parts having outer walls defining an envelope and an internal longitudinal wall dividing the envelope lengthwise, internal cross walls on opposite sides of the longitudinal wall forming liquid chambers opposite each other but separated by the longitudinal wall, there being a single chamber at each end of the 1ongitudinal wall and pairs of chambers on opposite sides of the longitudinal wall with the pairs on one side in staggered but in partially overlapping relation to the pairs on the other side of the longitudinal wall, passageways in the cross Wall between the individual chambers of each pair, external arcuate tubes having ends sealed respectively into the chambers opposite each other, inlet and outlet connections to the single chambers at each end of the longitudinal wall, a casing surrounding the manifold and its tubes, and inlet and outlet connections to the casing for conducting a fiuid through the casing in heat exchange relation with the manifold and tubes.

2. In a heat exchanger, a longitudinally split manifold comprising mating parts having outer walls defining an envelope and an internal longitudinal wall dividing the envelope lengthwise, internal cross walls on opposite sides of the longitudinal wall forming therewith separate liquid chambers, one of the chambers on one side of the longitudinal wall being opposite two adjacent chambers on the other side of the longitudinal wall, external arcuate tubes having opposite ends sealed to one of said mating parts and respectively into said two adjacent chambers and into said one chamber, a fluid inlet connection to one of said two adjacent chambers, a fluid outlet connection from the other of the two adjacent chambers, a casing surrounding the manifold and its tubes, and

inlet and outlet connections to the casing for conducting a fluid through the casing in heat exchange relation with the manifold and tubes.

3. In a heat exchanger, a manifold having mating parts with outer walls defining an envelope and with internal walls dividing the envelope into at least two separate in ternal liquid receiving chambers within said envelope, an inlet to one of the chambers, an outlet from the other of the chambers, external tubes having opposite ends sealed into and leading through the outer walls of one of the parts of the manifold and conducting the liquid from the inlet to the outlet chamber, a casing surrounding the manifold and its tubes, and inlet and outlet connections to the casing for conducting a fluid through the casing in heat exchange relation with the manifold and tubes.

4. In a heat exchanger, a cylindrical casing having an inlet connection at one end and an outlet connection at the other, semi-circular finned tubes within the casing centered on and extending crosswise of the longitudinal axis of the casing and spaced along the length of the casing, a manifold extending diametrically across and lengthwise of the casing and having openings therein sealed to opposite ends of the tubes, a liquid inlet at one end of the manifold, a liquid outlet at the other end of the manifold, and internal passageways within the manifold communicating with the manifold liquid inlet and outlet and connecting in a series groups of said tubes spaced apart along the length of the manifold.

5. The construction of claim 4 in which the manifold comprises two mating parts formed by flanges extending lengthwise of the casing and in which each of the manifold parts carries metal rings projecting radially outside the tubes and providing a support for the finned tube manifold assembly.

6. In a heat exchanger, a longitudinally split manifold having mating parts which when separated have inner surfaces which are accessible and when fastened together form a liquid distributing envelope, one of the parts having pairs of spaced openings extending through an outer wall thereof, a plurality of tubes each having opposite ends respectively extending through one and another of a pair of said openings and sealed into said openings, a liquid inlet to the manifold, a liquid outlet from the manifold, and internal walls on said one of the manifold parts forming internal passageways connecting said tubes in series between said inlet and outlet.

7. In a heat exchanger, a cylindrical casing having an inlet connection at one end and an outlet connection at the other, semi-circular finned tubes within the casing centered on and extending crosswise of the longitudinal axis of the casing and spaced along the length of the casing, said tubes being arranged in radially spaced tiers with the tubes of each tier nested into the tubes of an adjacent tier, a manifold extending diametrically across and lengthwise of the casing and sealed to opposite ends of the tubes, a liquid inlet at one end of the manifold, a liquid outlet at the other end of the manifold, and internal passageways within the manifold communicating with the manifold liquid inlet and outlet and connecting in a series groups of said tubes spaced apart along the length of the manifold.

References Cited in the file of this patent UNITED STATES PATENTS 722,717 Kiefer Mar. 17, 1903 1,061,295 Iaeger May 13, 1913 1,288,055 Langsenkamp Dec. 17, 1918 1,589,646 Hicks June 22, 1926 1,753,062 Nichols et al. Apr. 1, 1930 1,862,707 Rifenberick et al. June 14, 1932 1,897,997 Babcock Feb. 21, 1933 1,934,787 Bjorkland Nov. 14, 1933 

